OpaqueFunction

#launch   #argument   #ros2   #OpaqueFunction  

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Table of Content

OpaqueFunction

Action that executes a Python function.

demo

• Execute shell script using ExecuteProcess action
• Using OpaqueFunction to build shell script arguments
• Convert LaunchConfiguration to string using context.perform_substitution

shell script to execute

hello.zsh

#!/bin/zsh

echo $1 > /tmp/1

launch file

opa

from launch import LaunchDescription, LaunchContext
from launch.actions import ExecuteProcess, DeclareLaunchArgument
from launch.substitutions import LaunchConfiguration
from launch.actions import OpaqueFunction

SCRIPT_PATH = "/home/user/ros2_ws/src/pkg_launch_tutorial/scripts/hello.zsh"
ARG1="arg1"

def func_demo(context: LaunchContext, arg1: LaunchConfiguration):
    value = context.perform_substitution(arg1)

    if not value:
        value = "default value"
    run_script = ExecuteProcess(
        cmd=[[SCRIPT_PATH, " ", f"'{value}'"]],
        shell=True
    )
    return [run_script]



def generate_launch_description():
    ld = LaunchDescription()
    arg1 = LaunchConfiguration(ARG1)
    arg1_arg = DeclareLaunchArgument(
        ARG1, default_value="", description="arg1"
    )

    func_action = OpaqueFunction(function=func_demo, args=[arg1])

    ld.add_action(arg1_arg)
    ld.add_action(func_action)

    return ld